1. Field of the Invention
This invention relates to containers, and more particularly to self-locking containers which, once closed, cannot be opened without giving a visual indication of that fact.
Containers of the type here contemplated find a wide variety of applications. For example, in many jurisdictions, apartment dwellers or lessees are required to provide the landlord a key to their premises. These keys are often stored in readily available locations and tagged to identify the premises to which they provide access. Many tenants are uncomfortable with this requirement since they cannot know when or for what reason their premises have been entered, unless specifically advised. Thus, there is a need for a key storage system which will enable a tenant to know that access has been had to his key, and thus his premises; and, at the same time to store the key in a manner which will limit identification of the premises to which the key provides access.
2. Description of the Prior Art
A number of self-locking cartons or the like are known which are fabricated at least partially from cardboard or paperboard, as disclosed, for example, in U.S. Pat. Nos. 2,834,531 and 3,025,958. Containers of this type may be opened by cutting with a sharp, thin blade along a crease or corner and then reclosing them with a transparent adhesive or the like to prevent or delay detection of tampering.
Other containers employ a tear sheet to expose adhesive surfaces, as taught in U.S. Pat. No. 3,144,935, to gain access to the container contents, such containers being resealable, while U.S. Pat. No. 3,896,965 is directed to a tamper indicator tape for a hermetically sealed container, the tape being removable and changing color when flexed to indicate that the container has been tampered with. U.S. Pat. No. 4,197,94 discloses a transparent container cover which becomes opaque when flexed.
British Pat. No. 2,017,049 to Pierer discloses reusable sales packs, known as blister packs, that are opened without difficulty, i.e., without their permanent and visible destruction. The Pierer sales packs include a detent strip which, otherwise extending all round the lid, is interrupted at least in one corner zone so that opening the pack is facilitated.
French Pat. No. 7918535 to Burbon is directed to a container which is reusable numerous times for identical or similar articles, and which is opened without damage by the tool shown in FIG. 5.
Another self-locking container is the subject of copending U.S. Ser. No. 396,722, filed July 9, 1982 now U.S. Pat. No. 4,445,622. The non-reusable container therein disclosed comprises a first panel including a surface, the walls extending generally orthogonally from the surface, and a first cam with a locking surface; a second panel including a surface, walls extending generally orthagonally from the surface, and a second cam with a locking surface; the first and second cams being adapted to telescopically engage one another resiliently to flex one away from the other; the locking surfaces being adapted for mutual engagement to permanently lock the cams in mutual engagement; the side walls and walls being adapted to protect the cams and locking surfaces from disengagement; the first and second panels forming an enclosure which is permanently locked against entry upon completion of the telescoping movement, except by the permanent and visible destruction of the container.
The self-locking container of the present invention can be manufactured even more economically than the self-locking container of U.S. Pat. No. 4,445,622, since the present invention does not require a mechanical or cam activated mold, i.e., one with internal moving parts, to separate the undercut panels from the mold. This is accomplished by aligning all locking surfaces of each panel in one orientation, e.g., in the "x" direction, as latter described. Thus, the mold can be separated from each panel without the need for internal movable parts, thereby permitting a smaller mold, that in the manufacturing process can produce more containers in a given period of time.
Additional patents of interest are U.S. Pat. Nos. 579,560, 655,894, 2,734,624, 3,367,488, 3,527,400, 3,835,995, 3,924,746 and 3,949,931.